Tempering valve as HW Cylinder too hot.

[Ben-gee]

HW Cylinder is gravity, heating pumped therefore HW gets to boiler temperature. System is such that controls would be difficult add so I hope to add a tempering valve at the HW cylinder take off. This needs to be 22-22-22, am I on the right track and can you recommend one. I guess these must be common now due to thermal stores but I have no experience of them.

 

[Last Plumber]

HW Cylinder is gravity, heating pumped therefore HW gets to boiler temperature. System is such that controls would be difficult add so I hope to add a tempering valve at the HW cylinder take off. This needs to be 22-22-22, am I on the right track and can you recommend one. I guess these must be common now due to thermal stores but I have no experience of them.

Yes you can do that. That will be the most accurate way of controlling the Domestic hot water temperature in your situation.
The Cylinder should be at 60 deg C. What do you have it at now?

 

[ShaunCorbs]

There not very good for tank supply

 

[Last Plumber]

Where are you thinking of installing this?
Or are you getting a Plumber to do it?

 

[Ben-gee]

The cylinder has no controls so gets up to boiler temp, I measured it at a tap at 75 degC. I plan to fit on the 22mm hot coming out of the top of the cylinder before it goes anywhere. I thought to take a new dedicated cold feed in 22 from the CWS.
Yes it is on gravity open vented, do these not work well on this system?

 

[SimonG]

I'd be more inclined to install the necessary controls to control the issue at the source.
All that wasted energy.

 

[Ben-gee]

Fair point SimonG, I'm just thinking (not very hard by the look of it) at the moment. So far all over the phone and from memory, I installed an outside tap there a couple of years ago. I realise a visit is needed to have a proper look, I'm just considering theoretical options.

 

[Ben-gee]

Just for clarity, They measured tap temperature as 75 degC - not me personally.

 

[Last Plumber]

There not very good for tank supply

The cylinder has no controls so gets up to boiler temp, I measured it at a tap at 75 degC. I plan to fit on the 22mm hot coming out of the top of the cylinder before it goes anywhere. I thought to take a new dedicated cold feed in 22 from the CWS.
Yes it is on gravity open vented, do these not work well on this system?

As Shaun said, if you have low head (pressure) on the valve it will not work well. They have Non - return valves inside that take a certain amount of pressure to open.
Best practice is to install the correct controls but the simplest way to solve your issue is to install one of these.

It needs installing by a competent Heating Engineer/Plumber. If you install it in the wrong place it could be very dangerous.
I would not recommend doing it as a DIY job.
Your best bet is to get advice from someone who has seen the job.

 

[townfanjon]

Turn the boiler stat down for a start .

 

[Ben-gee]

Ok so I finally got to this job an Saturday. They've had someone there fiddling.
Set-up is; oil boiler downstairs in garage/basement (house on hill), CH pumped, HW gravity, programmer by boiler. They had said they didn't want to keep going down to operate programmer if needing to boost HW or put heating on early etc. Engineer had replaced room stat with a programmable roomstat and then set both HW and CH to always on and told them to leave it like that. There is no cyl stat for HW so basically boiler has been cylcing on/off permanently, boiler stat was on 75 deg C. This has killed one thermostatic shower cartridge and one Monsoon pump.
I turned boiler stat to 60 deg c and they have reported that now the water measures 60 at the taps, so that's better.
I have two questions.
1) Will 60 deg C be man enough to heat the house? I know it will do it, but more slowly.
2)If a cyl stat is fitted to turn off boiler when satisfied; when the heating comes on will the fact that this is pumped stop the cylinder from overheating , as presumably the CH pump takes most of the boilers output away from the gravity circuit? (this would allow the boiler stat to be turned up if proves necessary)
I also propose to extend the wiring to allow the original programmer to be sited in the house, as this seems sensible for their needs.

 

[SimonG]

How's the cylinder stat going to turn the boiler off when the heating us on. Gravity hot water is just that, pump takes nothing away.

S plan and fully pumped.

 

[Best]

Ideally as above and system converted to sealed if possible on oil or gas system